Not Applicable
Not Applicable
1. Field of the Invention
This invention pertains generally to medical devices for patient monitoring, and more particularly to a system for monitoring the orientation of an individual wherein remote indications of said orientation are generated.
2. Description of the Background Art
Injuries sustained from falls, such as by the elderly and patients within a medical facility, can be both debilitating and costly. The social and economic costs associated with falls in the elderly have been described as xe2x80x9cstaggeringxe2x80x9d and a xe2x80x9cpublic health problem of crisis proportionsxe2x80x9d (Hayes 1996). It is also a growing problem within the population as the fastest-growing segment of society are those over 65 years of age. Trends indicate that the nation""s senior citizens are becoming increasingly frail, functionally dependent, and more ill than their recent counterparts (Evans 1995).
One out of every three individuals over age 65, and half of those over age 80, experience a fall each year; this percentage equates to about 10 million US residents. Falls are the leading cause of injury deaths and disabilities in this age group (Kiely 1998, NINR 1994, Rubenstein 1994). Falls account for 87% of all fractures within individuals over age 65 and are the second leading cause of spinal cord and brain injury among older adults (CDC 2000b).
Hip fractures are a common injury sustained by the elderly during such falls. The current 34 million in this population group will double in the next 40 years, and it is clear that without effective intervention strategies, the number of hip fractures will increase as the U.S. population ages (CDC 2000c). Per statistics from the Centers for Disease Control and Prevention, the estimated $20 billion (1994) in US direct health care costs each year due to falls continues to rise at a rate faster than the elderly population is growing. A successful reduction in fall rate would thus predict significant potential for commercial success.
The situation is especially egregious for the most frail and ill of our elderly, currently about two million of us, that require full-time care in a skilled nursing facility. Within skilled nursing facilities the residents take an average of 7.2 medications (Evans 1995), and two out of three fall at least once each year (Cooper 1997, Evans 1995). The majority of falls among the elderly within skilled nursing facilities occur in their own rooms as they attempt to get up out of the bed, without assistance, to use the lavatory at night (Alcee 2000, Capezuti 2000, Evans 1998).
In addition, numerous cases of falls occur among those with mental disorders. As many as 90% of the residents of skilled nursing facilities suffer from some form of mental disorder, including dementia (Evans 1995). An individual suffering from any form of mental confusion, whether endemic or due to the effect of medication, is subject to an increased risk of falling due to the associated impairment of judgment, lack of visual-spatial perception, loss of ability to orient themselves geographically (Rubenstein 1994), inability to understand, or impaired memory functions (Evans 1998).
In the past, patients considered to be at a high risk of falling were often restrained to their beds to prevent unassisted egress; however, it will certainly be appreciated that such treatment is contrary to the dignity of the patient. Furthermore, the use of restraints is generally impractical and it is often illegal (Health Care Reform Act of 1994). Another drawback is the inherent difficulty in attempting to accurately identify individuals that have a high likelihood of falling.
A variety of protective garments and protection devices have been studied for reducing fall-induced injuries, in particular hip fractures. In one such device, protective pads are retained proximal to the greater trochanter (upper portion of the hip bone), within a garment to displace the impact forces of a fall. Wearing these protective garments has been shown to provide a measure of protection against hip fractures, however, a large percentage of patients either refuse to wear the protective garments or become non-compliant with regard to use over time.
Recently, individuals have been monitored utilizing devices in which the individual or patient is harnessed to the monitoring device by means of wiring. These devices can be cumbersome and often restrain the movements of an individual. The benefits derived from monitoring the position and/or movement of an individual or patient have long been appreciated, and a number of monitoring devices have been considered.
The effectiveness of current devices for monitoring position or activity has been limited for several well-known reasons. Often such devices are unreliable as they rely on pendulums, mercury switches, or other forms of mechanisms that do not provide reliable detection. The majority of these devices are prone to the generation of false positives due to these inherently unreliable sensing mechanisms. Ultimately, as a result of the false alarms, the wearer or caregiver becomes conditioned to ignore the alarm, thereby negating any possible benefits that may have otherwise been derived. Unreliable sensing is particularly troublesome for devices that are not directly worn by the subject, such as pressure-activated devices, that indirectly infer subject orientation or activity.
As a group, the devices can be difficult to operate, or their operation may be suitable only for limited clinical use. A level of cognitive functioning and mental alertness is often required of those wearing the devices. This limitation can preclude the use of these devices for a substantial percentage of potential users who may be confused, disoriented, or unconscious and thus unable to activate the device.
Devices that are worn directly by a subject tend to be large, bulky, awkward, and/or uncomfortable which limits user acceptance and concomitant use. Several devices are further limited with regard to their applicability, as they may need to be worn by the human subject in a way that restrains the individual and/or compromises human dignity. Limited mobility is one particularly strong objection to many such devices which require the subject to be xe2x80x9cattachedxe2x80x9d to the device by way of restrictive harnesses, belts, tethers, cords, cuffs, bracelets, elastic bands, or the like.
Devices requiring the aforementioned attachments are not suitable for continuous wear by an individual, and periodic disconnection is required to accommodate a number of activities, such as bathing. The restriction of movement caused by these devices is obtrusive and can noticeably interfere with sleep or daily activities. Not surprisingly, the interference that need be endured when using these devices compromises their acceptance and effectiveness. The relatively high cost of the these devices is often further exacerbated by their associated methods of use which subject the devices to both damage, such as from inadvertent washing, and from theft. A further complication often arises after one of these devices becomes damaged or otherwise needs to be disposed of, because the commonly used mercury switches within the devices present a special waste disposal requirement that can be particularly challenging within a health care facility.
Attempts to solve the foregoing problems employing an assortment of electromechanical alarms have been largely met with failure. The actual liability associated with falls is so high that we see increasing use of these devices, apparently just to make patients and their families feel like xe2x80x9csomethingxe2x80x9d is being done, even though they are costly and ineffective. One of these problematic devices attempts to monitor the bed, or floor area near the bed, for changes in applied force. The device was found to generate false positives while being difficult to maintain and cumbersome. Independent reviews of additional devices currently on the market have concluded that no device exists which has been successful at reducing the rate of falls, and that a portion of these device types were actually associated with an increase in the incidence of falls.
The drawbacks associated with the current monitoring devices are regrettable in view of the serious nature and sheer number of injuries which are sustained from falls. Applicable subjects for attitude monitoring include a wide range of patients, and in particular those recovering from surgery or stroke, those under the influence of medications, elderly individuals in a weakened condition or suffering from dementia, or normally active individuals whose temporary condition has placed them at risk of falling. It will be appreciated that subject movement may be involuntary, such as in the case of sleepwalking, and that serious injuries may result from such movement due to a fall or the dislodgment of medical devices, which may include fluid supplies, air supplies, drainage connections, or monitoring devices. One commonly cited condition of those experiencing a fall is an altered mental state; therefore, it will be appreciated that if a device is to be successful it should not require cognitive functioning on the part of the user for activation.
Monitoring the physical activity of a subject can provide benefits within a number of applications. These include patient safety, activity studies on humans, studies on laboratory animals, compliance programs for postoperative rehabilitation or physical therapy, ensuring proper posture or sleeping position, preventing patients from becoming ambulatory without assistance, detecting subject loss of consciousness, controlling post surgical movement, or determining whether set levels of activity are being achieved.
Therefore, a need exists for a non-cumbersome device that is capable of providing reliable monitoring of subjects without the aforementioned drawbacks that are inherent in current devices. The present invention satisfies those needs, as well as others, and overcomes the deficiencies of previously developed attitude indicators and monitoring devices.
The present invention provides a device and method of monitoring the orientation of an individual with a miniature attitude-sensing unit capable of communicating orientation alerts for registration on a receiver unit. Registration comprises reception followed by identification, attitude recognition, or activity characterization, along with displaying, annunciating, or logging the transmitted conditions. The attitude-sensing unit comprises an orientation sensor and signal transmitter that are attached to the individual being monitored, preferably on the thigh of the individual. It should be appreciated that although the subject is typically human, the subject may alternatively comprise an animal under medical care or study, or an object in association with a human, or animal, possibly under medical care or study. The attitude indicator and activity-monitoring device of the present invention may additionally be referred to herein as an xe2x80x9cattitude indicating devicexe2x80x9d, or simply xe2x80x9cdevicexe2x80x9d, and it generally comprises an attitude transmitter unit coupled with a receiver unit.
By way of example and not of limitation, one embodiment of the present invention provides for monitoring the orientation of a human subject based on the orientation of a specific portion of the subject""s body upon which the attitude transmitter unit has been positioned. One aspect of the invention is the transmission of alert signals based on a comparison between the orientation of the attitude transmitter unit, which is attached to the body of the subject individual, and a predetermined set of orientation criteria. If the orientation criteria are met, an alert is generated from the attitude transmitter unit to a receiver unit capable of indicating the alert condition. For example, the detection of rapid declination may be indicative of a fall.
A preferred application of the attitude indicating device is that of detecting intended egress by an individual. To detect patient egress, such as from a bed or wheelchair, an attitude transmitter unit is integrated within an appliance that is preferably attached to the posterior thigh, of the individual being monitored. An attitude receiver unit is located within range of the attitude transmitter unit to receive alert conditions and generate an indication of the alert in a form that may include, audio, visual, or tactile information. By way of example, the transmitter generates radio-frequency alert transmissions in response to changes in transmitter attitude that are characteristic of specific conditions. The alert transmissions are received by a receiver unit that generates audio alerts to attendants, or other nearby personnel.
The receiver unit may be configured to provide attitude, or activity, indication in a variety of forms, such as audible tones and/or words, discrete visual indicators, such as LEDs, various displays such as an alphanumeric LCD, or by remotely conveying attitude, or activity, information to another system. An example of conveying the information to a remote system may involve interfacing the attitude indication signals with an institutional monitoring system, such as a nurse""s station capable of displaying the attitude information as status information, of generating audible alerts, of dispatching personnel, of generating a page, and so forth. It will be appreciated that the receiver unit may comprise more than one device; for example, a receiver positioned at a first location and operably connected to circuitry at a second location that performs the processing of the received signals. The circuitry at the second location may in turn be operably connected to another unit, and so forth. Any combination or level of integration can be supported insofar as one or more of the units, or devices, is capable of generating alerting signals that are responsive to the transmitter unit.
The attitude, and activity, indicating device of the present invention allows physical orientation to be indicated as a set of measurements, or by way of orientation alerts generated in response to attitude threshold conditions. Attitude and activity are preferably detected within the transmitter by utilizing an acceleration sensor that is capable of detecting attitude (tilt), and positional rate of change. An attitude transmitter configured to provide attitude measurements may transmit measured orientation information either in response to status changes or on a periodic basis. Alerting signals may be generated upon the measured conditions meeting one or more alert validation criteria. The receiver unit is capable of responding to the transmitted signals in a manner consistent with the application. For example, the receiver may generate an audio output in response to the alert signal, or it may record, display, communicate, and/or analyze the attitude or acceleration data contained within a transmission.
In a basic application of the attitude indication device, the attitude transmitter unit generates an alert signal when the thigh of the patient changes from a generally horizontal plane, as would exist for a patient lying in bed, to a specific downward angle characteristic of the patient getting out of bed in preparation for walking. The attitude transmitter unit may additionally be configured for generating periodic signals, such as measurements, or an xe2x80x9calivexe2x80x9d signal. In the absence of measurements, or status changes, being transmitted to the remote unit, an alive signal may be periodically transmitted to provide an indication to the remote attitude receiver unit that the attitude transmitter is still xe2x80x9calivexe2x80x9d, insofar as it is operating properly and remains within reception range. When configured to receive a periodic alive signal, the attitude receiver unit is capable of generating an alert to personnel if the transmitter unit has left the vicinity (reception range) of the receiver, or has experienced a malfunction. It should be appreciated that alive signal generation is preferably combined with the use of alert signal generation, so that alerts may be detected in response to events while the conveyance of periodic status information is accommodated to provide notification of undesired patient ambulation or system failures.
The attitude indicator device of the present invention may be utilized within a variety of diverse medical applications, which include but are not limited to: preventing/detecting patient egress, preventing/detecting patient falls, monitoring infants, detecting the onset of labor in horses, tracking physiological activity of patients, use in physical therapy, detecting range of motion, monitoring epileptics for seizures, limiting post surgical patient movement, limiting the motion of unconscious patients recovering from surgery, monitoring for sleep apnea and snoring, alerting employers of unsafe worker activity, detecting improper standing sleeping or lifting posture, and detecting lapses of consciousness.
The attitude receiver unit can be adapted to provide alerts and attitude monitoring to suit a variety of environments, which for instance may include: in-room alarms, remote alarms, wearable alarms, and institutional alarms. The attitude receiver unit may be configured to generate an indication to personnel that comprises one or more forms of output generated from a visual, audible, or tactile feedback source. The feedback alerts the wearer and/or supervisory personnel of subject conditions for which an action may be indicated, examples of which are subject egress or attempted ambulation. The output of an attitude receiver unit configured to receive attitude measurement information may additionally be connected to a data-logging unit to provide for future analysis. Furthermore, the attitude receiver unit may be integrated into various standard communication systems, such as those connected to the Internet, as well as pagers, cellular phones and various wireless communication protocols, such as those based on the Bluetooth standard. The receivers may also be integrated into custom or institutional communication systems, such as systems associated with a nurse""s station or other systems designed to support the alerting of personnel.
The attitude transmitter unit of the present invention comprises an orientation sensor coupled to a radio-frequency (RF) transmitter. The orientation sensor is preferably implemented as an acceleration sensor, although alternative means for sensing positional attitude in up to three dimensions may be utilized. In an aspect of the invention, the threshold conditions under which an alert signal is to be generated by the attitude transmitter unit may be set according to the particular application being addressed. The attitude transmitter unit embodied herein is small, lightweight, wireless, waterproof, shockproof, unobtrusive to the wearer, may be worn continuously for several consecutive days, and does not require that the wearer be cognitively functional. It can be adhered to various body parts according to the requirements of the medical application being addressed, or incorporated into clothing, headgear, bandages, inanimate objects, and so forth. Communication between the attitude transmitter unit and an attitude receiver unit is preferably by way of a radio frequency link; however, alternate forms of communication may be employed, comprising forms such as inductive coupling, infrared, ultraviolet, audio, and ultrasonic.
The present design further anticipates an embodiment of the attitude transmitter that utilizes a transponder mechanism, such as an RF transponder, wherein the receiver (or other external device) is configured to generate a first transmission to which the transmitter responds with a responsive second transmission. The power for the transmitter and attitude sensing circuits are thereby derived from the received power of the first signal, wherein no batteries need to be provided within the transmitter. The available transmitter operating power derived from a transponder circuit is, however, limited in that an alternative acceleration sensor having a lower power dissipation is necessary to provide reliable operation.
The attitude receiver unit may be configured so that the individual wearing the attitude transmitter unit is alerted to the attitude conditions, wherein the device provides real-time feedback that is capable of training a wearer to maintain a desired position, or range of positional attitudes. Patient feedback can be especially useful with postoperative patients directed to limit certain forms of movement during the recovery process. The attitude transmitter unit is also configured for detecting its own removal from the body of the individual to which it is attached, whereupon it preferably generates an alert signal so that the associated attitude receiver unit can generate an indication, such as an audible alarm.
Attitude indication devices can be configured for a stand-alone system wherein a single transmitter is associated with a single receiver in combination, or may alternatively be integrated into a custom or existing receiver/annunciation system and configured to receive data from any number of attitude transmitter units. The attitude transmitter unit may be manufactured in an array of shapes and sizes in accord with specific applications, while the preferred solid-state design anticipates further miniaturization to facilitate both unobtrusive attachment and/or implantation. In addition, when an attitude transmitter unit is no longer necessary, or serviceable, it may be either recycled or disposed of without environmental impact considerations (such as the special handling requirements of mercury switch-containing devices).
Subject attitude is preferably determined within the attitude transmitter unit by way of a solid-state orientation sensor capable of providing orientation information in relation to the portion of the individual""s body to which it is attached. It will be appreciated that integrated circuit sensors, such as acceleration sensors, are generally still considered to be xe2x80x9csolid-statexe2x80x9d devices although they often incorporate micro-electromechanical systems (MEMs). A solid-state orientation sensor that registers orientation measurements is preferred over the use of a mechanical switch that is generally limited to a non-linear on/off mode of response. The output of a mechanical switch is not generally well suited for medical attitude/activity monitoring due to the large proportion of false alarms generated and the difficulty involved with qualifying a discrete event that is subject to mechanical vibration, inertia, and electrical noise.
A preferred solid-state orientation sensor comprises an acceleration sensor configured to register acceleration in at least one plane of motion. When retained in a static orientation, the acceleration sensor provides orientation data in response to the force of earth""s gravitation, the resulting static force being up to one gravitation (G) unit on any of the three axes. In contrast to a tilt sensor, the acceleration sensor additionally provides rate of change information that may be utilized to further qualify prospective events. Therefore, it will be appreciated that the data provided by the acceleration sensor within the attitude transmitter unit can be used to enhance the accuracy of attitude or activity information, whether detecting patient falls, attempted egress, slips, transmitter removal, seizures, as well as other situations that may be characterized in relation to positional attitude and changes thereto.
An object of the invention is to provide a device capable of indicating and monitoring the physical attitude of an individual.
Another object of the invention is to provide a reliable solid-state device for sensing positional attitude in up to three dimensions.
Another object of the invention is to provide a reliable wireless device for monitoring the positional attitude of an individual.
Another object of the invention is to detect patient egress and to communicate an associated alert to mitigate the risk of falls.
Another object of the invention is to provide selection of the angle of displacement for which the device will produce a desired alert signal.
Another object of the invention is to provide a device and method of sensing subject attitude as may be applied to human, non-human, and inanimate subjects (objects).
Another object of the invention is to provide a device that may be reused or disposed of without special environmental or waste handling requirements.
Another object of the invention is to provide a monitoring device that is small, lightweight, and unobtrusive.
Another object of the invention is to provide a robust monitoring device that is not easily damaged or broken, and whose method of use reduces the probability of detachment, loss or theft.
Another object of the invention is to provide a device that is waterproof and shockproof.
Another object of the invention is to provide a low-cost device which may be readily disposed of when no longer needed, or serviceable.
Another object of the invention is to provide a monitor that is compatible with the activities of a human subject, such that it may be worn for several consecutive days without the need of restricting the subject from bathing, showering, and so forth.
Another object of the invention is to provide a monitoring device whose use does not require the wearer to be cognitively functional.
Another object of the invention is to provide a monitor that may be worn on various body parts according to the needs of the user, or incorporated into such items as medical appliances, rehabilitation appliances, trusses, clothing, shoes, or headgear.
Another object of the invention is to provide an attitude monitoring system that provides a wireless connection between an attitude detector and a remote attitude indication unit so that wearers need not be xe2x80x9ctetheredxe2x80x9d by an electrical cord to an electrical device.
Another object of the invention is to create a device capable of providing real-time feedback so that a wearer may be conditioned to maintain a desired positional attitude, or range of motion, without the necessity of constant supervision.
Another object of the invention is to provide a monitoring device that is compatible with both stand-alone systems, wherein one transmitter is associated with one receiver, and integrated (institutional) systems wherein signals from multiple transmitters are detected by one or more receivers.
Another object of the invention is to provide a monitoring device capable of transmitting a signal, or data, to either stationary or portable receiver systems (nearby or remote), depending on the needs of the user.
Another object of the invention is to provide a device that may be manufactured in various sizes in accordance with the intended application, and in particular which may be miniaturized for implantation purposes.
Another object of the invention is to provide an attitude monitoring device which is capable of measuring both static and dynamic acceleration to properly distinguish events, for example, it is able to distinguish between an individual changing sleeping positions and attempted egress.
Another object of the invention is to provide an attitude transmitter unit configured to detect when it is being removed from a subject, whereupon it responds by generating an alerting signal.
Another object of the invention is to provide a monitoring device that can be readily manufactured at low cost.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.